Transaction Language 1 (TL1) is a widely used management protocol in telecommunications. TL1 is a cross-vendor, cross-technology, man-machine language, and is widely used to manage optical (SONET) and broadband access infrastructure in North America. TL1 may be used in input and output messages that pass between Operations Support Systems (OSSs) and Network Elements (NEs). NE vendors may implement TL1 in their devices to communicate with OSSs.